Tools: Extensions of the Body

I originally heard about this on Scientific American's 60-Second Science podcast: Tool-use induces morphological updating of the body schema.

You have to register to read the full article, but the abstract is as follows:

To control bodily movements the human brain relies on a somatosensory representation referred to as the body schema. The almost century-old hypothesis that tool-use induces plastic changes resulting in the tool being incorporated in the body schema is nowadays widely accepted. Whether this somatosensory representation is truly modified remains unknown, however, as tool-use has never been shown to affect arm motor behaviour. Here we report that using a mechanical grabber that physically extends the arm does alter the kinematics of subsequent free-hand grasping movements. Remarkably, tool-use after-effects generalise to pointing movements, despite the absence of specific tool-training. Furthermore, this effect is driven by an increase of the represented length of the arm: after tool-use, subjects localised touches delivered on the elbow and middle fingertip of their arm as if they were farther apart. These findings indicate that tool-use alters the body schema, and also show that what is modified is the somatosensory representation of intrinsic properties of the body morphology.

Essentially, your brain appears to assimilate tools that you are using into your body schema, treating them as extensions of your limbs. Even after the tool is put down, it takes a few minutes for it to leave the body schema.

Not being a biologist (or having read much more than the abstract at this point), I'm a little reluctant to push this too far. But it's interesting.